1. Field of the Invention
This invention relates broadly to telecommunications. More particularly, this invention relates to mappers/demappers for the transmission of data streams across different protocols.
2. State of the Art
Ethernet is a widely implemented local area network (LAN) and metropolitan area network (MAN) transmission standard. Ethernet is an asynchronous variable length packet based system. SONET, which stands for Synchronous Optical Network, is a set of ANSI telecommunications standards which specify a modular family of rates and formats for synchronous optical networks. SONET provides a plesiochronous standard operating environment for managing high bandwidth services, and incorporates multiplexing, service mapping, and standardized interfaces. ATM, which stands for Asynchronous Transfer Mode, is defined by a set of ATM forum recommendations which specify mechanisms for transporting data in cells of a predetermined number of bytes.
Currently, when it is necessary to move data from an Ethernet protocol environment to a SONET network, the Ethernet data is converted into ATM standard format which is then modified to meet SONET standard format, as ATM shares some commonalities with each of Ethernet and SONET. However, this is inefficient as it results in additional overhead and additional complexity. There is no known solution for mapping and demapping Ethernet packet traffic directly onto and from a SONET network.
It is therefore an object of the invention to provide a device which maps/demaps Ethernet traffic directly onto and from a SONET network.
It is another object of the invention to provide a device which can be implemented on a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC) to directly map/demap Ethernet packets to SONET data and SONET data to Ethernet packets.
It is a further object of the invention to provide a device which is modular and can be implemented in an FPGA or ASIC.
In accord with these objects, which will be discussed in detail below, a bridging device for mapping Ethernet data packets directly onto a SONET network and demapping SONET data into Ethernet data packets is provided. The bridging device includes an Ethernet controller (chip set) which receives packet data, a SONET framer for a SONET interface, a Utopia Level 2P (Fr-UTOPIA) interface for the SONET framer and an FPGA (or ASIC) which bridges the Fr-UTOPIA interface and a system bus interface of the Ethernet controller.
The FPGA is preferably implemented in VHDL software code as several modules: an Ethernet controller interface module, a chunk memory implementation module, a UTOPIA interface module, a microprocessor interface module, and an Fr-UTOPIA OUT module. The Ethernet controller interface module interfaces with the data and control signals from a thirty-two bit data bus of the Ethernet controller and writes the data to chunk memory implemented in the FPGA. The chunk memory implementation module implements the chunk memory to a programmable size of 32, 48 or 64 bytes, which supports point-to-point protocol (PPP) for mapping internet protocol (IP) data, and includes a memory address generator to read and write the memory. The UTOPIA interface module implements an interface with data and control bus signals of Fr-UTOPIA and reads data sixteen bits at a time from chunk memory and writes the data to the Fr-UTOPIA interface bus. The microprocessor interface module implements the control and status registers. The Fr-UTOPIA OUT module implements address and data bus drivers and control signals of the Fr-UTOPIA data bus. A top level module defines all external pins, signals used internally, and the above five modules, and instantiates the modules with proper interconnecting signals.
The bridging device of the invention permits Ethernet data packets to be directly mapped onto a SONET network and SONET network data to be demapped into Ethernet packets.
Additional objects and advantages of the invention will become apparent to those skilled in the art upon reference to the detailed description taken in conjunction with the provided figures.